1. Field of the Invention
An embodiment of the present invention relates to a plasma CVD apparatus for forming a semiconductor film. Further, an embodiment of the present invention relates to a method for forming a crystalline semiconductor film using a vapor deposition method and a method for manufacturing a semiconductor device including the crystalline semiconductor film.
2. Description of the Related Art
In a technical field of thin film transistors, a plasma chemical vapor deposition (plasma CVD) method which is used for formation of a semiconductor film is employed, and various improvements have been attempted to manufacture products with higher yields.
For example, an electrode structure of a plasma CVD apparatus is disclosed where an electrode for generating plasma in a reaction chamber is provided with cylindrical recessed portions and the cylindrical recessed portions are connected to each other through a groove which is narrower than the diameter of the cylindrical recessed portion (see Patent Document 1).
In addition, disclosed is a gas diffuser plate (a so-called shower plate) having a gas flow path, the diameter, depth, and surface area of which gradually increase toward an edge portion from a center portion, for dispersing gas in a treatment chamber and forming films uniform in thickness and characteristics (see Patent Document 2). As another example, disclosed is a technique for forming a film under the following conditions for forming higher quality films more efficiently: a ladder-like electrode is used; an ultra high-frequency power of 100 MHz is supplied with a gas pressure of 400 Pa; and a film formation rate is set to 2 nm/second with a distance of 6 mm between the ladder-like electrode and a substrate (see Patent Document 3).